My recent and aged brass is unaffected. Gunner is fixing my Lionel GG-1 thanks to the investment of Henning's trains making the side Foam does not touch my models. Tissue paper only.
FWIW, I find a lot of old brass that's falling apart at the solder joints.
This thread is really hard to watch. I've seen zinc pest with most of the major train makers new and old. If the mixture and casting temperatures are not right, it sets up sites for future corrosion. You can go back to Ives tenders in the late 1920's, most of anything that McCoy made with zinc alloy castings, and now examples from all the major train makers, MTH, Atlas, Lionel, Williams, KLine
Jim
Let's face it, it's a casting process that unless carefully controlled will result in a limited lifetime. We've known this for decades.
Not just limited to Pre War or Modern Era. I have had to rebuild four Postwar Lionel Turbines. Here is the latest, from a month ago, a 682. By far the worst zinc pested frame/chassis I have seen.
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Update on my Williams GG-1: after ordering a replacement shell, I received an email this morning notifying me my purchase was refunded. A fresh look at the parts site now shows all GG-1 shells as sold out. (Fortunately, my Williams 681 shows no signs of the pest... yet.). Time to look for a suitable GG-1 replacement 
